Chair back



FIG. 1 is an isometric view of a chair back incorporating our newdesign, wherein the phantom lines illustrate environment and form nopart of the claimed design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a rear elevation view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is a left side elevation view thereof, the right side elevationview being a mirror image.

The broken lines shown in FIGS. 3 and 5 are for illustrative purposesonly and form no part of the claimed design.

FIGS. 2 through 6 have been shown on an enlarged scale with respect toFIG. 1.

The ornamental design for a chair back, as shown and described.